Issue with 'Unknown Error: -512'

[Garrett Cooper]

On Mon, Jul 18, 2011 at 5:19 PM, Brandon Falk <falkman at gamozo.org> wrote:
> On 7/18/2011 10:18 AM, Andriy Gapon wrote:
>>
>> on 18/07/2011 17:53 Brandon Falk said the following:
>>>
>>> Hello,
>>>
>>> In recent branches (confirmed with 224119) builds compiled with clang
>>> happen to
>>> throw 'Unknown error: -512' in a lot of places, making the system
>>> unusable.
>>> (Untested on gcc compiled systems). Originally I thought the problem was
>>> with
>>> specific programs, then I narrowed it down to file I/O, and now I've
>>> narrowed it
>>> down to open() with O_TRUNC. Without O_TRUNC there seems to be no issues
>>> whatsoever. With O_TRUNC on open() it fails with that 'Unknown error:
>>> -512' every
>>> other time you run the program. Common issues, portsnap is affected,
>>> making it
>>> impossible to fetch/extract ports. As well as redirecting output in
>>> shells eg
>>> `echo 'hi'>  test` fails every other try. You have the same issue with
>>> text
>>> editors like `edit` where it fails every other save. There are no issues
>>> with
>>> `echo 'hi'>>  test` as there is no O_TRUNC, it only seems to be an
>>> O_TRUNC error.
>>>
>>> Any tips? Otherwise I'll be looking into this today myself.
>>
>> Just a hint that you could try using DTrace syscall and fbt providers to
>> see where
>> in kernel (if in kernel) that -512 return value originates.
>>
>
> Update:
>
> I've traced more and more into the kernel, and currently I have found the
> following trace:
>
>>>> ufs_setattr() (in sys/ufs/ufs/ufs_vnops.c:507)
> (In truncate a bunch of stuff is done, but it succeeds until VOP_SETATTR)
>>>> vn_truncate() (in sys/kern/vfs_vnops.c:636)
>>>> kern_openat() (in sys/kern/vfs_syscalls.c:1043)
>>>> kern_open()   (in sys/kern/vfs_syscalls.c:1035)
>>>> open() (in sys/kern/vfs_syscalls.c:1006)
>
> ufs_setattr() returns with -1 (EPERM)
>
> I'll continue to try to find the exact problem. A quick workaround currently
> would probably be to use a different filesystem other than ufs, but then
> again, I have no clue if other filesystems have the same issue.
>
> Hopefully that trace will help anyone who wants to help out.

What UFS options do you have defined in your kernel?
Thanks,
-Garrett